Dynamic interactions between bicycles and rumble strips

The rumble strips have proven to provide a good protection against the run-off-the-road type of accidents. However, installing them on the local and community roads has raised many concerns among the cyclists. The cyclists occasionally cross over the rumble strip patterns in order to avoid obstacles or debris on the road shoulders or pass a slower moving rider. The majority of the reported concerns are those regarding the ride comfort and controllability of a bicycle traversing the rumble strip patterns. The ride discomfort and controllability of a bicycle traveling on the rumble strips are experimentally investigated by considering a comprehensive test matrix involving: (1) the conventional and suspended bicycles; (2) different rumble strip patterns and traversing speeds; (3) oblique angle of approach to rumble strip; (4) multiple trials and (5) seven test subjects. The objective assessment of the ride comfort on the rumble strip patterns is carried out by measuring the acceleration responses of the bicycle frame at the handle bar and the seat post while the controllability of the bicycle is assessed in terms of the measured yaw oscillations of the handle bar. The cyclist's sensation of the rumble strip patterns is further investigated through subjective measurements where the riders rated each test based on different criteria involving the ride comfort and controllabilit

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Χρηματοοικονομικές αγορές, ανάπτυξη της αγοράς χρήματος στη Σερβία

Το βασικό κίνητρο για την εργασία αυτή ήταν ότι, στη Σερβία μετά από τις ριζικές αλλαγές του πολιτικού και οικονομικού συστήματος που έγιναν το 2000, δεν εκπονήθηκε κάποια μελέτη σχετικά με την ανάπτυξη της αγοράς χρήματος. Η εργασία περιλαμβάνει μία ιστορική ανασκόπηση και ανάλυση της αγοράς χρήματος στη Σερβία από το 1975 μέχρι το 2005, καθώς και την ανάλυση του μακροοικονομικού και μικροοικονομικού περιβάλλοντος της χώρας το οποίο έχει καθοριστικό ρόλο στην ανάπτυξη του χρηματοοικονομικού συστήματος. Η ανάλυση έδωσε ιδιαίτερη έμφαση στην περίοδο 2000 - 2005, στην οποία ξεκίνησαν οι πιο σημαντικές μεταρρυθμίσεις στο πολιτικό, νομοθετικό και το οικονομικό πλαίσιο της Σερβίας. Η ανάλυση αυτή είναι καθοριστική αναφορικά με την διατύπωση προτάσεων για την ανάπτυξη της αγοράς χρήματος στη Σερβία. Στην επιδίωξη των στόχων της εργασίας υπήρχαν πολλές δυσκολίες και περιορισμοί. Ειδικότερα η εργασία απαιτούσε τη μελέτη ενός ιδιαίτερα μεγάλου αριθμού παραγόντων και φορέων οι οποίοι διαδραματίζουν καθοριστικό ρόλο στην ανάπτυξη της αγοράς χρήματος. Έτσι, δεν ήταν δυνατή μία βαθιά και λεπτομερής ανάλυση, επειδή για κάθε παράγοντα και φορέα της αγοράς χρήματος μπορεί να απαιτείται μια ξεχωριστή μελέτη. Επίσης υπήρχαν δυσκολίες στη συλλογή στατιστικών στοιχείων σχετικά με τους συμμετέχοντες, τον όγκο, τις χρονικές διάρκειες των συναλλαγών και τα διατραπεζικά επιτόκια στην αγορά χρήματος στη Σερβία

Characterisation of biomedical titanium layers deposited by a vacuum plasma spray process

In this paper we will describe the process of the deposition of thick layers of VPS-Ti coating, which is used as a bonding layer for the upper porous Ti coatings on implant substrates. In order to deposit the powder, we used HoGANaS Ti powder labelled as AMPERIT 154.086-63 mu m. In order to test the mechanical properties and microstructure of the VPS-Ti coating, the powder was deposited on C 4171 (X15Cr13 EN10027) steel substrates. Mechanical tests of the microhardness of the coating were per-formed by the Vickers hardness test method (HV0.3) and tensile strength by measuring the force per unit area (MPa). The micro-hardness of the coating is 159 HV0.3, which is consistent with the microstructure. The coating was found to have a good bond strength of 68 MPa. The morphology of the powder particles was examined on a scanning electron microscope. The microstructure of the coating, both when deposited and etched, was examined with an optical microscope and a scanning elec-tron microscope. By etching the coating layers, it was found that the structure is homogeneous and that it consists of a mixture of low-temperature and high-temperature titanium phases (alpha-Ti + beta-Ti). Our tests have shown that the deposited layers of Ti coating can be used as a bonding layer for porous Ti coatings in the production of implants

A coupled thermo-mechanical model of friction stir welding

A coupled thermo-mechanical model was developed to study the temperature fields, the plunge force and the plastic deformations of Al alloy 2024-T351 under different rotating speed: 350, 400, and 450 rpm, during the friction stir welding process. 3-D FE model has been developed in ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law, and the Coulomb’s Law of friction. Numerical results indicate that the maximum temperature in the friction stir welding process is lower than the melting point of the welding material. The temperature filed is approximately symmetrical along the welding line. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface. With increasing rotation speed, the low plastic strain region is reduced. When the rotational speed is increased, the plunge force can be reduced. Regions with high equivalent plastic strains are observed which correspond to the nugget and the flow arm

Mechanical and structural characteristics of atmospheric plasma-sprayed multifunctional tio2 coatings

Titanium dioxide (TiO2) is a multifunctional oxide that is an interesting material for many technological applications. This paper presents the mechanical properties and microstructure of TiO2 coatings resistant to dry sliding friction, corrosion, grain abrasion and erosion of particles at operating temperatures up to 540 degrees C. Layers of TiO2 coatings have been successfully deposited on test samples of steel C.4171 (X15Cr13 EN10027) using the atmospheric plasma spray (APS) process with plasma gun distances of 100 mm and 110 mm from the substrate. The APS procedure is used to produce relatively thick coatings of biocompatible and antibacterial TiO2 ceramic coatings for orthopedic applications. The coatings were deposited using the Plasmadyne company plasma spray system and Metco TiO2 powder, whose particles have an angular morphology produced by the melting and grinding cast blocks. The evaluation of the mechanical properties of the layers was made using the microhardness testing method HV0.3 and the tensile bond strength by tension testing. The analysis of the microstructure of the sprayed TiO2 coating layers was made in accordance with the Pratt & Whitney standard, using optical microscopy (OM). The morphology of the powder particles, the surface of the deposited coating and the coating fractures were examined by scanning electron microscopy. Tests have shown that the layers of TiO2 coatings deposited with a plasma spray distance of 110 mm have good mechanical properties and microstructure, which allow its use in the development of biomedical implants